Results

In a showdown with AstraZeneca, Pfizer posts solid — and very familiar — PhIII breast cancer data for talazoparib

Jennifer Litton, MD Anderson Cancer Center

Pfizer $PFE came through with positive numbers for its Phase III study of its PARP inhibitor talazoparib in advanced breast cancer — lining up right alongside AstraZeneca’s $AZN leading rival Lynparza. And the results position Pfizer to join the PARP lineup as the fourth player to toe up to the market threshold — though maybe not in the lead position it was promised when the pharma giant bought the drug last year.

Analysts have been waiting to see how Pfizer’s drug, bagged in the $14 billion acquisition of Medivation, will fare relative to the competition. It’s a widely frowned on approach by the experts, but market analysts love to match up data from two different studies of the same disease, offering caveats on what could be important distinctions in trial designs, patient populations and endpoints.

In this case, which begs for a comparison, the numbers are close enough to Lynparza’s readout earlier in the year that it will likely emphasize just how comparable these therapies can be, including the competition at Tesaro $TSRO (Zejula) and Clovis $CLVS (Rubraca).

Pfizer’s researchers concluded that there was a 45.8% reduction in the risk of disease progression in the EMBRACA study, which recruited women with HER2-negative breast cancer with germline BRCA mutation. Median PFS was 8.6 months, compared to 5.6 months in the control arm.

The overall response rate was 62.6% in the drug arm compared with only 27.2% in the control. There were also 12 complete responses — no visible signs of the disease — for talazoparib, compared to none in control.

“Most notable for this study was not only the improvement to date of PFS, but the time to clinical deterioration, which was 24.3 months for patients on talazoparib, versus 6.3 months for those on standard-of-care chemotherapy,” MD Anderson’s Jennifer Litton noted.

Compare that to Lynparza’s 42% reduction in the risk of progression, a 7-month versus 4.2-month PFS — or a gap of 2.8 months versus 3 months for talazoparib — and a 59.9% talazoparib vs 28.8% chemo ORR.

Both studies compared their drug against standard of care chemo.

Former Medivation CEO David Hung sold this drug hard in driving the deal to sell his company to Pfizer for $14 billion last year, claiming it was clearly superior to everything out there. That would be an even harder sales job today, with the late-stage data on display.

Michael Schmidt didn’t see much daylight between what Pfizer and AstraZeneca have on offer, and he considers that a plus for Clovis.

Talazoparib was previously touted as potential “best-in-class” PARP inhibitor and most potent “PARP trapper”. That said, at least based on the preliminary data disclosed in PFE’s (MP)press-release this morning, results in breast cancer look rather similar to AZN’s (MP) OLYMPIAD trial results of Lynparza which were presented earlier this year at ASCO. We think this bodes well for CLVS. Positive EMBRACA data provides addl. validation for PARPs in breast cancer, however potential lack of meaningful clinical differentiation and hence a credible competitive threat by talazoparib should read through positively for CLVS.

Tesaro launched the Phase III BRAVO study to see how their drug performed in a similar breast cancer population, but noted back in March that it couldn’t serve as a registration study after patients bowed out, preferring to get a marketed PARP rather than chemo. The biotech went on to say that it is studying its drug in combination with a checkpoint therapy in breast cancer.

Image: Shutterstock


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